The silicon epitaxial wafer is manufactured as follows.
(Transferring Step)
A silicon wafer substrate is placed on a blade (transfer table) of a transfer robot and transferred from a buffer chamber to the above of a susceptor (processing table) in an epitaxial growth furnace (heat treatment chamber). At the time of transferring, the interior of the epitaxial growth furnace is previously heated to a certain temperature (transferring temperature) by lamp heating.
(Placing Step)
The silicon wafer substrate on the blade is lifted by lift pins. The blade is externally retracted from the epitaxial growth furnace. The susceptor is moved up to place the silicon wafer substrate on the susceptor. Thus, the silicon wafer substrate is moved from the blade onto the susceptor.
(Heat Treatment Step)
Then, the silicon wafer substrate is heated by lamp heating up to a temperature (>1100° C.) suitable for vapor phase growth. And, material gas for forming an epitaxially-grown film is flown along the front surface of the silicon wafer substrate. Thus, a thin film of the same silicon epitaxial growth layer is formed on the front surface of the silicon wafer substrate.
With the advance of miniaturization and high resolution of the semiconductor device in these years, the crystal quality demanded for the epitaxial silicon wafer has become high, and a high yield is also demanded.
Originally, the crystal quality of the epitaxial growth layer is considerably higher than that of the silicon wafer substrate, and the epitaxial growth layer is considered to be a defect-free layer which is free from a grown-in defect.
But, the process (placing step) of placing the silicon wafer substrate on the susceptor by transferring into the epitaxial growth furnace has a problem that the silicon wafer substrate is warped.
Specifically, when the silicon wafer substrate is transferred from the buffer chamber having normal temperature into the epitaxial growth furnace which is previously heated to a transferring temperature, the silicon wafer substrate suffers from a sudden temperature change to form a sudden temperature gradient, causing an inconsistency of a thermal stress. If the inconsistency of the thermal stress exceeds a critical point, the individual portions of the silicon wafer substrate are warped to have a concave shape. The warping affects adversely on the quality of the silicon epitaxial wafer. Therefore, the following measures have been taken to avoid it.
(Conventional Technology Described in Patent Literature)
Patent Literature 1 points out a problem that if the silicon wafer substrate is warped while it is being lifted up by the lift pins, the wafer back surface is rubbed by the lift pins having a rough contact surface, and scratches or particles are generated on the wafer back surface. In order to prevent the warping from occurring, the heating lamps above the epitaxial growth furnace are turned off to keep the furnace interior in a low temperature state, the silicon wafer substrate is placed from the blade onto the susceptor, and the upper heating lamps are turned on to perform epitaxial growth. Patent Literature 1 processes the silicon wafer substrate having a diameter of 150 mm (paragraph (0033) of Patent Literature 1). It is also considered that the silicon wafer substrate has a low temperature of merely 400° C. at the time when the silicon wafer substrate is placed to the susceptor (paragraph (0027) of Patent Literature 1).    Patent Literature 1: JP-A 2000-269137